This invention relates, in general, to power dividers and combiners used in microwave systems, and more particularly, to wide-band power dividers and combiners which can be incorporated on a single miniature integrated circuit (I.C.) chip.
Powder dividers are used to take a signal at a common terminal and divide the signal among a series of signal paths while maintaining desired impedances at the common terminal and at all output terminals. The same apparatus can be used as a power combiner by feeding signals to each of the signal paths and combining these signals at the common terminal.
Conventional power dividers generally utilize quarter-wave transmission lines in their signal paths. These dividers are often referred to as Wilkinson power dividers since they incorporate isolated, branch waveguide power dividers as disclosed in U.S. Pat. No. 3,091,743 to Wilkinson. Wilkinson power dividers have good isolation between their output terminals. The bandwidth of Wilkinson power dividers is increased by cascading additional sections of the power divider, each section incorporating a quaterwave length transmission line. A correlation between bandwidth ratio and number of sections incorporating quarterwave length transmission lines is given in the following table which was developed by Seymor B. Cohn in "A Class of Broadband Three-Port TEM-Mode Hybrids", IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-16, No. 2, February 1968.
TABLE 1 ______________________________________ Sections 2 3 4 7 ______________________________________ Bandwidth Ratio 2.0 3.0 4.0 10.0 (x:1) ______________________________________
Thus, as the bandwidth increases, the size of the divider increases. Because of the increasing size of the divider with increasing bandwidth, Wilkinson type dividers with large bandwidths cannot readily be miniaturized to fit on a single chip.
Recent developments in technology have allowed the size of many electronic components to be reduced. The size of products using these components are undesirably increased if large dividers must be included therein. Hence, broadband Wilkinson dividers have become impractical for miniature applications. Some power dividers have been designed which replace transmission lines with discrete lumped element components. However, these have not had the bandwidth associated with cascaded Wilkinson dividers, and in fact, are limited to very narrow bandwidths. The prior art, therefore, has not provided a power divider with a broad bandwidth which can be miniaturized to fit on a single I.C. chip.